This invention relates to a high speed facsimile transmission system and more particularly to a toner image-fixing device used with such a system to fix unfixed toner images on a record medium.
Conventional facsimile transmission systems consume the time period of from 4 to 6 minutes for transmitting, a manuscript prepared on a piece of paper having a size of A4 (210mm .times. 297mm) according to Japanese Industrial Standards (JIS) through a telephone line. In order to economically utilize the telephone line, high speed facsimile transmission systems for decreasing the transmission time have been required and particular in long distance transmission. In order that a manuscript such as above described can be transmitted within a time period on the order of one minute through a telephone line, the existing facsimile transmission systems include the band compressor to be adapted to read and write that portion of the manuscript having a high information density at a low speed while reading and writing that portion thereof having a low information density and a blank portion thereof at a high speed. On the receiver side, therefore, electrostatic latent images are formed on a record medium fed intermittently and at different speeds as determined by a band compressed signal from an associated transmitter. For example, the record medium may have a feed speed variable from 0.1 to 70 millimeters per second. That is, the feed speed has a maximum magnitude equal to seven hundred times its minimum magnitude. Thus it has been difficult to completely fix developed toner images on a record medium having such a large change in feed speed.
Conventional fixing devices involve the open type, the hot plate type the type utilizing a flash lamp etc. When used in fixing toner images on a record medium intermittently fed at different speeds as above described, those devices have been dis advantageous in the following respects: In the open type devices for melting and fixing the toner images in an atmosphere of heated air, the record medium being suspended or fed at an extremely low speed may contact heat too much to be yellowed or scorched. On the contrary, the feed at a high speed may cause a phenomenon that the toner image is not yet fixed. The hot plate type devices are good in thermal efficiency as compared with the open type devices, but when the record medium cut into predetermined sizes is used with such devices, the end portions of cut medium are apt to be put in poor contact with the hot plate with the result that toner images on the end portions thereof poorly contacted by the hot plate remain unfixed. In addition, waiting time is required until the devices exhibit the desired fixing ability and therefore they must remain heated. Thus the temperature within the devices is raised leading to a fear that the particular circuit components and the characteristics of a toner used are deteriorated. Finally, in flush lamp type, the fixing operation is performed without any delay time but in view of repeated lighting times, the optical output has been required to be relatively high in order to effect always the complate fixing.
In conventional high speed facsimile transmission systems there has not yet provided suitable fixing means for continuously fixing toner images on the record medium fed intermittently and still at different speeds. This has resulted in the necessity of performing the two stage operation in which the record medium bearing electrostatic latent images thereon is temporally stocked without passing through the fixing device until the latent images have been completed to be formed on the record medium after which the latent images are developed and fixed at a predetermined constant speed on the record medium. This measure has required additional means for holding the record medium until the formation of electrostatic latent images is completed, feeding the record medium to developing and fixing devices after the formation of the latent images have been completed and controlling the holding and feeding means and developing and fixing devices. Therefore the resulting system has been inevitably large-sized and expensive.
Accordingly it is an object of the present invention to provide in a facsimile receiver for forming electrostatic latent images intermittently and at different speeds in response to a band compressed signal transmitted thereto, a new and improved toner image-fixing device for successively and continuously fixing toner images, developed with a magnetic toner on a record medium having the electrostatic latent images formed thereon and fed at said different speeds.
It is another object of the present invention to provide a new and improved toner image-fixing device including a source of flash light, for fixing toner image on each portion of a record medium having a predetermined length at a time thereby to successively and continuously fix all the toner images on the record medium.
It is still another object of the present invention to provide a new and improved toner image-fixing device including a plurality of a hog plates disposed along a run of a record medium to preliminarily heat toner images on the record medium being fed.